Light-weight magnesium alloys having excellent specific strength and specific rigidity are being studied as constituent materials of various parts, such as housings for mobile electronic devices, including cellular phones and laptop computers, and parts of automobiles, including wheel covers and paddle shifts. Magnesium alloy parts are mainly made of cast materials manufactured by a die-casting process or a thixomold process (AZ91 alloy as defined in the American Society for Testing and Materials standards). In recent years, parts manufactured by press forming of a sheet made of a wrought magnesium alloy exemplified by AZ31 alloy as defined in the American Society for Testing and Materials standards have been used for parts, such as the housings. Patent Literatures 1 and 2 disclose press forming of a rolled sheet manufactured under particular conditions from AZ91 alloy or an alloy that has substantially the same Al content as AZ91 alloy.
It is believed that magnesium has excellent vibrational energy absorption characteristics. For example, alloys having a reduced Al content and Zn-free alloys, more specifically, AM60 alloy as defined in the American Society for Testing and Materials standards, are used as constituent materials of parts that require high impact strength, such as parts of automobiles.